Sound radiator



AP-fil 16, 1929. R. v. l.. HARTLEY 1,709,073

- SOUND RADIATOR Filed June 19, 1923 @Slg y fuffa/@a A@ Patented pr. 16, 1929.

UNITED STATES PATENT OFFICE.

RALPH V. L. HARTLEY, F SOUTH ORANGE, NEW JERSEY,` ASSIGNOR T0 WESTERN ELEQTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Application filed .Tune 19,

This invention relates to sound radiators and has for an object to set up in the air cylindrical sound waves particularly of low tones.

This is accomplished by providing a sound radiator in the form of. a cylinder to which is applied torsional vibrations in accordance with the electric currents to be converted into sound waves, or v1ce versa,

depending upon whether the diaphragm is used as a receiver or as-a transmitter. The torsion is applied in such a manner that substantially all parts of the cylinder expand and contract simultaneously, whereby cylindrical sound waves are emitted. Incase 1t is desired that the diaphragm emphasize low tones, the len h of the receiver should be comparable with the wave length of such tones and, for instance, may be three feet long in order to eiliciently emit the freuencies found in the low part of the voice requency range.

For further details of the invention reference may be made to the drawings .wherem Fig. 1 is a plan view of a cylindrlcal radiator serving as a loud speaking receiver andto the center of which torsion is applied by means of an electric dri-ve. Fig. 2 is a side elevation partly in section of Fig. 1 taken at Referring in detail to Fig. 1, the cylindrical radiator 1 may be of thin, stili' librous material such as paper, cloth, or the like, or of metal, and is rigidly supported at its extremities by the rings 2 and 3 carried by the base 4. The rings 2 and 3 are suitably fastened to the base, for instance, by means of screws 5 which extend into the base 4 through suitable apertures in the extensions 6, 7, 8 and 9 of the rings.

Connected to the center of the dlaphragm is a band 10 which is fastened at diametrically opposite points by means of rods 11 and 12 to the armature 13 of an electromagnet receiver 14, which receives the electric currents to be converted into sound waves. These electric currents may vary in accordance with speech or other sound waves to be reproduced. The receiver 14 is as described in Egerton Patent No. 1,365,898 January 18, 1921, except that rod 12 and spring 15 for counteracting the torsion of the cylinder have been added. The recelver 1 4 may be suitably supported on the basel 4 soUNn RDIATOE.

1923. serial No. 946,309.

by means not shown. The armature 13 is plvotally supported at its center as described in the patent above. The band 10 is fastened to the cylinder so that the cylinder and the band 10 carried thereby, due to the inherent resiliency of the material of the diaphragm, have a tendency to move in the direction of the arrow. This normal tension at the center of the cylinder is opposed by means of the spring 15. No support at the bottom of the bandv 10 is disclosed in the drawings, although such a support may be employed if desired.

The cylindrical radiator, in effect, comprises two ruled surfaces, the elements of the diaphragm surface at each side of the band 10 being straight lines.v The result' of moving the band 10 in the direction of the arrow is to makeV each of the half portions move in the direction in which they will as' sume a truly'cylindrical shape, result of moving the band 10 in the opposite direction, if this motion were suiliciently great, which it is not in practice, would cause the center of each of the half portions to reduce in diameter to practically zero and form the apices of two cones having their bases in the band 10 and the rings 2 and 3.

Since substantially all parts of the radiator increase or decrease in diameter simultaneously, cylindrical sound Waves will be set up in the surrounding air.

With a vibrating diaphragm of the usual type in the form of a disc or the like, low frequencies can be efficiently reproduced only .by making the diaphragm large in all directions normal to the direction of vibration, therebypreventing the air fromleakingaroundthe edges, so to speak. In the case of the cylindrical radiator according to the present invention, however, the radial motion of the air will be the same at all polnts around any crosssection, and hence, there will be no tendency for the air to flow around, and no marked loss of .eiliciency' results from making the diameter small compared to the wave length. The length of the radiator in this case, however, should be comparable withthe wave length, in or-l wherea's, the

, ,1 der to ericiently reproduce frequencies in the neighborhood vof fifty c cles per second. The overall length ,ofthe iaphragm may be of the order of three feet, the diameter approximately six inches or less. y

If desired the cylinder 1 may be filled with fibrous material such as cotton, wool or the like, to reduce sound vibrations of the enclosed air.

What is claimed is:

1. A hollow sound radiator, the length of which is comparable to the wave length in the low part of the voice frequency range, and means lfor applying torsion to said sound radiator in accordance with the vibrations to be reproduced.

2. A tubular sound radiator, the length o1 which is comparable to the wave length'in the low part of the voice frequency range, and torsional driving means connected thereto.

3. A tubular sound radiator, the length 'of which is comparable to the wave length in the low part of the voice frequency range, and driving means connected thereto.

4. A hollow tubular sound radiator of light elastic material, the length of which is large in comparison to the diameter and the length of which is' com arable to the Wave length in the low part o the voice frequency range.

5. A long narrow paper cylindrical sound radiator, means spaced a art for rigidly clam ing said radiator, an other means locatedp between said first mentioned means for twisting'said radiator in accordance with sound waves.

In witness whereof, I hereunto subscribe my name this 13 day of June A. D., 1923.

RALPH V. L. HARTLEY. 

